1. Field of the Invention
The present invention relates to a very hard and tough molded article for working metals, hard metals, ceramics and glasses. The molded article is sintered and made of boron carbide and a binder metal.
2. Background of the Art
Boron carbide is particularly resistant to sand blasting, a fact suggesting certain uses for boron carbidecontaining sintered articles. Heretofore, however, such sintered articles were characterized by low resistance to breakage. For example, Kieffer, R. K. and Schwarzkopf, P., Hartstoffe und Hartmetalle [Hard Substances and Hard Metals], published by Springer-Verlag, 1953, compared wear values of hard metals and hard substances determined according to the sand blasting method on pages 524 and 525. The wear value of a sintered article containing 95% weight percent boron carbide (B.sub.4 C), i.e., 20 weight % C, and 5 weight % iron was the lowest reported in the comparison thereof with sintered articles made of tungsten carbide-cobalt (WC-Co), titanium carbide-iron-chromium (TiC-Fe-Cr) and titanium carbide-vanadium carbide-iron-nickel (TiC-VC-Fe-Ni). Further, page 327 of the publication reported that attempts at binding B.sub.4 C with tough metals had failed.
Further, if B.sub.4 C particles are mixed with powders of known binder metals cobalt (Co) or nickel (Ni), sintering thereof is known to result in undesirable chemical reactions and the formation of unwanted phases therein, for example, boride phases. The different physical characteristics between the already existing phases and the newly developed phases frequently produce cracks and gaps in the molded article as early as during cooling.